As vacuum-based coating methods, known methods of applying metal layers to the surfaces of substrates are physical gas deposition methods or PVD (Physical Vapor Deposition) methods. The starting material, that is to say, the coating material is thereby converted to the gas phase with the aid of physical methods. The gaseous material condenses on the substrate to be coated, thereby forming the target layer or coating. Various methods are used to vaporize the starting material. The starting material can, for example, be converted to the gas phase by cathode deposition or sputtering. The term “sputtering” is hereafter understood to mean “sputter deposition”, which is commonly used to produce thin layers. Sputtering of thin layers is employed, for example, to refine surfaces.
The very low process temperatures of PVD coating methods make it possible to use low melting plastics materials. The surface of a plastics substrate or plastics structural component is not, however, usually sufficiently free of flaws. A primer must therefore usually be applied beneath the PVD layer. Two-component solvent-based primers are usually used for this purpose, such as polyurethane primers, which require thermal drying. The usual drying conditions are 80° C. over a period of 30 minutes. A thermally drying primer is not, however, suitable for the build-up of relief structures. A metal layer applied by means of the PVD process is moreover not sufficiently mechanically stable for some applications, such as in the interior of an automobile. For this reason, another layer is usually applied to the metal layer, for example, a clear lacquer.
The metal layer is also difficult to decorate via the known coating systems. The application of patterns or characters is only possible via a laser treatment of the clear lacquer. Laser writing is, however, expensive and spoils or damages the surface of the clear lacquer. Laser treatment also leads to the formation of open edges, which in a moist atmosphere can be the cause of infiltration, as a result of which the entire structure of the coating is weakened. The additional laser treatment is not possible in in-line processing. This method also cannot reproduce any relief structures.